1. Field of the Invention
The present invention relates to an ink-jet water-based ink set for recording images by ink jetting with the aid of inks of at least two colors; to an ink-jet water-based ink set for recording images by color ink jetting with the aid of inks of at least four colors such as yellow, magenta, cyan, and black; and to an ink-jet recording method for recording images by spraying this ink set in fine liquid drops.
2. Description of the Related Art
With an ink-jet recording method, ink drops are formed and deposited partially or completely on paper or another recording material to record images by electrostatic attraction, by mechanically vibrating or displacing the ink with piezoelectric elements, by heating the ink to form gas bubbles and utilizing the resulting pressure, and other types of ink ejection.
In conventional practice, the inks for such ink-jet recording methods include those obtained by dissolving or dispersing water-soluble dyes or pigments in solvent media composed of water or combinations of water and water-soluble organic solvents.
As ink-jet printers become more advanced and widespread, problems are encountered in terms of different colors blending (bleeding) together in adjacent areas and the print quality being adversely affected when color images are recorded, particularly on the copy paper or other types of plain paper used in offices and households. Such bleeding presents a particularly serious problem in the case of yellow and black inks because they have markedly different tones.
Using inks obtained by adding surfactants or other permeability-enhancing compounds to the ink base has been proposed in Japanese Patent Application Laid-Open No. 55-65269 as a means of addressing these problems. According to another method, disclosed in Japanese Patent Application Laid-Open No. 8-209049, a composition containing sodium alginate as a gel-forming seed is combined with a composition containing calcium cations as gelation initiators to prevent the compositions from mixing with each other as a result of gelation reactions. Another common method adopted in conventional practice for commercially available color ink-jet printers entails suppressing bleeding by mixing the ink with an alkyl ether of a polyhydric alcohol, such as diethylene glycol monobutyl ether, as a penetrant.
The above-described prior art has the following drawbacks, however. Adding surfactants or admixing polyhydric alcohol alkyl ethers is still not sufficiently effective in terms of bleeding suppression, and, furthermore, the enhanced ink penetration causes monochromatic images to blur and makes it more difficult to obtain sharply defined edges. Utilizing gelation reactions is disadvantageous in the sense that the choice of materials is severely limited because most coloring agents form insoluble salts with calcium cations.
In addition, bleeding and other print quality attributes depend greatly on the type of paper because the plain paper used in offices and households varies considerably in terms of fiber thickness or length, the type and amount of the filler (or sizing agent), and the like.
An object of the present invention, which was achieved in order to address the aforementioned problems of the prior art, is to provide an ink-jet water-based ink set that allows bleeding to be efficiently prevented when images are recorded on various types of plain paper. Another object of the present invention, is to provide an ink cartridge containing the ink-jet water-based ink set, and a recording method using the is the ink-jet water-based ink set.
According to a first aspect of the invention, an ink-jet water-based ink set used for an ink jetting recording apparatus is provided, which comprises:
a first ink containing water, a first coloring agent and a first component; and
a second ink containing water, a second coloring agent and a second component which causes an endothermic reaction when in contact with the first component.
According to a second aspect of the invention, an ink cartridge used for an ink jetting recording apparatus is provided, which comprises:
a first compartment accommodating a first ink which contains water, a first coloring agent and a first component;
a second compartment accommodating a second ink which contains water, a second coloring agent and a second component which causes an endothermic reaction when in contact with the first component.
According to a third aspect of the invention, an ink-jet recording method for recording images by ejecting an ink-jet water-based ink set onto a recording medium, is provided, which comprises:
ejecting a first ink containing water, a first coloring agent and a first component onto the recording medium; and
ejecting a second ink containing water, a second coloring agent and a second component onto the recording medium, the second component causing an endothermic reaction when in contact with the first component.
In the ink-jet water-based ink set, the cartridge or the recording method according to the invention, the first component may be barium hydroxide and the second component may be an ammonium salt. Ammonium hydroxide may be produced by the reaction of the barium hydroxide and the ammonium salt. The ammonium salt may be at least one salt selected from a group consisting of ammonium chloride, ammonium nitrate, and ammonium thiocyanate. The first coloring agent may be a black coloring agent and the second coloring agent may be a yellow coloring agent.
The ink set or the cartridge may include third and/or fourth ink, each of which includes a component which causes an endothermic reaction when in contact with the first component. In this case, the third ink may contain a magenta coloring agent, and the fourth ink may contain a cyan coloring agent. A solid deposit may be formed upon the endothermic reaction of the first component with the second component. The first ink may contain 0.01-10 wt % of the first component and the second ink may contain 0.01-10 wt % of the second component.